Our long-term goal is to understand the genetics, evolution and mechanism of color vision by a combination of molecular, electroretinographic, and statistical approaches. Our current aims are: 1. To study (a) the origin of X-linked genes for the red and green pigments (opsins) in humans, and (b) the antiquity of the three alleles (red, yellow and green) at the single X-linked opsin locus in the squirrel monkey (a New World monkey). 2. (a) To study the hypothesis that the 600 bp sequence located 4 kb upstream from the red opsin gene is a locus control region, and (b) to identify potential regulatory sites in the 500 bp region upstream from each opsin gene. 3. To find out whether (and to explain why) the blue opsin (autosomal) locus is monomorphic in humans and in squirrel monkeys, in contrast to the existence of highly polymorphic X-linked pigment variants in humans and monkeys. 4. To study (a) the structure/function relationships in color pigment proteins, (b) whether the nocturnal life of Galago crassicaudatus (a prosimian) has led to relaxed selection pressure on the color opsin genes, and (c) whether the color opsins have been well conserved in the tree shrew (Tupaia belangeri), a dichromat extremely well-adapted to diurnal life (>96% cones). To achieve these aims we propose to pursue the following work: 1. To sequence (a) introns 2 and 4 of the human red and green opsin genes, (b) the red, green and yellow alleles at the X-linked locus in squirrel monkeys, and (c) the color opsin genes in the gal ago and the tree shrew, including the 500 bp promoter region of each gene. 2. To determine its presence and, if so, to sequence the hypothesized LCR region in the squirrel monkey, the galago and the tree shrew. 3. To sequence the coding regions of the blue opsin gene in 15 humans and 15 squirrel monkeys. Determine the spectral absorption peak of each new variant. 4. To conduct statistical analyses of the new and published opsin DNA sequence data.